/* ----------------------------------------------------------------------
 * Project:      CMSIS DSP Library
 * Title:        arm_merge_sort_f32.c
 * Description:  Floating point merge sort
 *
 * $Date:        2019
 * $Revision:    V1.6.0
 *
 * Target Processor: Cortex-M and Cortex-A cores
 * -------------------------------------------------------------------- */
/*
 * Copyright (C) 2010-2019 ARM Limited or its affiliates. All rights reserved.
 *
 * SPDX-License-Identifier: Apache-2.0
 *
 * Licensed under the Apache License, Version 2.0 (the License); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an AS IS BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "arm_math.h"
#include "arm_sorting.h"


static void topDownMerge(float32_t *pA, uint32_t begin, uint32_t middle, uint32_t end, float32_t *pB, uint8_t dir)
{
	/* Left  array is pA[begin:middle-1]
	 * Right Array is pA[middle:end-1]
	 * They are merged in pB
	 */

	uint32_t i = begin;
	uint32_t j = middle;
	uint32_t k;

	// Read all the elements in the sublist
	for (k = begin; k < end; k++) {
		// Merge
		if (i < middle && (j >= end || dir == (pA[i] <= pA[j]))) {
			pB[k] = pA[i];
			i++;
		} else {
			pB[k] = pA[j];
			j++;
		}
	}
}

static void arm_merge_sort_core_f32(float32_t *pB, uint32_t begin, uint32_t end, float32_t *pA, uint8_t dir)
{
	if ((int32_t)end - (int32_t)begin >= 2) {         // If run size != 1 divide
		int32_t middle = (end + begin) / 2;           // Take the middle point

		arm_merge_sort_core_f32(pA, begin,  middle, pB, dir);  // Sort the left part
		arm_merge_sort_core_f32(pA, middle,    end, pB, dir);  // Sort the right part

		topDownMerge(pB, begin, middle, end, pA, dir);
	}
}


/**
  @ingroup groupSupport
 */

/**
  @addtogroup Sorting
  @{
 */

/**
   * @param[in]  S          points to an instance of the sorting structure.
   * @param[in]  pSrc       points to the block of input data.
   * @param[out] pDst       points to the block of output data
   * @param[in]  blockSize  number of samples to process.
   *
   * @par        Algorithm
   *               The merge sort algorithm is a comparison algorithm that
   *               divide the input array in sublists and merge them to produce
   *               longer sorted sublists until there is only one list remaining.
   *
   * @par          A work array is always needed. It must be allocated by the user
   *               linked to the instance at initialization time.
   *
   * @par          It's an in-place algorithm. In order to obtain an out-of-place
   *               function, a memcpy of the source vector is performed
   */


void arm_merge_sort_f32(
	const arm_merge_sort_instance_f32 *S,
	float32_t *pSrc,
	float32_t *pDst,
	uint32_t blockSize)
{
	float32_t *pA;

	/* Out-of-place */
	if (pSrc != pDst) {
		memcpy(pDst, pSrc, blockSize * sizeof(float32_t));
		pA = pDst;
	} else {
		pA = pSrc;
	}

	/* A working buffer is needed */
	memcpy(S->buffer, pSrc, blockSize * sizeof(float32_t));

	arm_merge_sort_core_f32(S->buffer, 0, blockSize, pA, S->dir);
}
/**
  @} end of Sorting group
 */
